1. Field of the Invention
The present invention relates to a temperature control device and a temperature control method that utilize a thermoelectric module to perform temperature control of an object of temperature control such as an ink-jet head, and an ink-jet recording apparatus.
2. Description of the Related Art
In general, in order to control an object of temperature control to remain at a fixed temperature, a temperature control device is used in various apparatuses. As an example of an object that is subject to temperature control by such a temperature control device, for example, an ink-jet head mounted on an ink-jet recording apparatus can be cited.
In the ink-jet head of the ink-jet recording apparatus, temperature changes due to a change in environmental temperature, heat at the time of driving, or the like, and ink filled inside the ink-jet head causes a temperature change. Since a viscosity of the ink in the ink-jet head changes in accordance with this temperature change, a temperature control device for controlling the ink-jet head to a predetermined temperature is provided in order to discharge ink drops from nozzle openings always with an identical ink viscosity to maintain an optimal ink discharge characteristic.
Here, a conventional temperature control device used in an ink-jet head will be described with reference to FIG. 13. Note that FIG. 13 is a schematic block diagram of a temperature control device in accordance with the prior art.
As shown in FIG. 13, one surface of a thermoelectric module 302 is air-tightly adhered and fixed with satisfactory heat conduction to an ink-jet head 301 of an ink-jet recording apparatus as an object of temperature control. A radiator (or heat sink) 303 is air-tightly adhered and fixed with satisfactory heat conduction to the other surface of the thermoelectric module 302 in the same manner.
In addition, a temperature sensor 304 is attached to the ink-jet head 301. This temperature sensor 304 is connected to a temperature detection unit 305 and outputs temperature information of the ink-jet head 301 to a control unit 306 from the temperature detection unit 305.
Here, the control unit 306 controls a driving unit 307 according to a temperature difference between a temperature of the ink-jet head 301 and a target temperature, thereby controlling a driving current flown to the thermoelectric module 302 to cause the thermoelectric module 302 to perform heating or cooling drive and control the temperature of the ink-jet head 301 to be the target temperature.
As described above, in the conventional temperature control device, the temperature sensor 304 is attached to an object of temperature control to measure a temperature, and the thermoelectric module 302 is air-tightly adhered and fixed to the object of temperature control to adjust an amount of its driving current, whereby a temperature of the object of temperature control is controlled to be a target temperature.
In the above-mentioned conventional temperature control device, since an object of temperature control is subjected to temperature control with high accuracy using a thermoelectric module, it is necessary to detect a temperature of the object of temperature control accurately. For this purpose, a temperature sensor has to be attached with satisfactory heat conduction in a place where a temperature of the object of temperature control can be detected accurately. In addition, the thermoelectric module has to be air-tightly adhered and fixed with satisfactory heat conduction to the object of temperature control.
However, if the thermoelectric module is air-tightly adhered and fixed with satisfactory heat conduction to the object of temperature control consisting of an ink-jet head or the like and the temperature sensor is further attached, since a place for attaching the temperature sensor is limited depending on a form and a dimension of the object of temperature control, the temperature sensor cannot be air-tightly adhered and fixed, with satisfactory heat conduction to, a place where a temperature can be detected accurately. Consequently, there is a problem in that a temperature of the object of temperature control cannot be detected accurately by the temperature sensor and the object of temperature control cannot be subjected to temperature control with high accuracy.
In this way, when temperature control of the object of temperature control cannot be performed with high accuracy, if the object of temperature control is an ink-jet head, there is a problem in that temperature control of ink in the ink-jet head cannot be performed with high accuracy by the temperature control device and a printing quality degrades.
Moreover, in order to prevent influence of an ambient temperature or influence of condensation, the temperature control device may be formed in a closed structure depending on an object of temperature control. However, there is a problem in that a place for attaching the temperature sensor is further limited by forming the temperature control device in a closed structure, a place for detecting a temperature accurately is eliminated, and a thermal resistance is further increased, so that target temperature control of high accuracy cannot be performed.
In particular, if the object of temperature control is an ink-jet head, since a difference between a temperature at the time when it is used and a temperature at the time when it is not used is large, condensation appears evidently, and the temperature control device may be formed in a closed structure in order to prevent influence of an ambient temperature and condensation. However, since a place for attaching the temperature sensor is further limited by forming the temperature control device in a closed structure and the temperature sensor cannot be air-tightly adhered and fixed with satisfactory heat conduction to the ink-jet head, there is a problem in that an ink temperature cannot be controlled to be a target temperate with high accuracy because a temperature cannot be detected accurately.
In addition, in an object of temperature control that is detachably attachable to an apparatus main body in order to replace the object of temperature control due to failure or the like, in the case where it is desired to reuse a temperature sensor, there is a problem in that, if the temperature sensor is attached to the object of temperature control, the temperature sensor has to be removed from the object of temperature control and the removal takes a long time.
In particular, in the case of an ink-jet head, the ink-jet head is replaced due to failure, wear or the like of it, and the ink-jet head itself is constituted to be detachably attachable to an apparatus main body. There is a problem in that, if a temperature sensor is attached to the ink-jet head, the temperature sensor is removed from the ink-jet head in order to reuse it and the removal takes time.
In view of such circumstances, it is an object of the present invention to provide a temperature control device and a temperature control method that are capable of applying temperature control of high accuracy to an object of temperature control and facilitating removal of the object of temperature control to reduce costs at the time of replacement, and an ink-jet recording apparatus.
A first aspect of the present invention for solving the above-mentioned problems resides in a temperature control device that is characterized by including a thermoelectric module having an object of temperature control air-tightly adhered to its one surface; driving means for flowing a driving current to the thermoelectric module; temperature difference detecting means for obtaining a Seebeck voltage, which is generated from a temperature difference on both the surfaces of the thermoelectric module when the driving current is not flowing, to output a temperature difference signal; temperature detecting means for outputting a temperature detection signal based on a signal of a temperature sensor that is thermally coupled to the other surface of the thermoelectric module; and controlling means for controlling the driving means so as to set the object of temperature control to a target temperature according to the temperature detection signal and the temperature difference signal.
A second aspect of the present invention resides in a temperature control device that is characterized by further including, in the first aspect, switching means for alternately switching a connection state of the thermoelectric module and the driving means and a connection state of the thermoelectric module and the temperature difference detecting means.
A third aspect of the present invention resides in a temperature control device that is characterized in that, in the first or second aspect, the controlling means controls an amount and a direction of the driving current that the driving means supplies to the thermoelectric module.
A fourth aspect of the present invention resides in a temperature control device that is characterized in that, in any one of the first to third aspects, the object of temperature control is an ink-jet head.
A fifth aspect of the present invention resides in a temperature control device that is characterized in that, in any one of the first to fourth aspects, a radiator is air-tightly adhered to the other surface of the thermoelectric module.
A sixth aspect of the present invention resides in a temperature control device that is characterized in that, in any one of the first to fifth aspects, a P-type thermoelectric element and an N-type thermoelectric element are connected in series or in serial parallel in the thermoelectric module.
A seventh aspect of the present invention resides in an ink-jet recording apparatus that is characterized by including the temperature control device in any one of the first to sixth aspects.
An eighth aspect of the present invention resides in a temperature control method for having an object of temperature control air-tightly adhered to one surface of a thermoelectric module, and at the same time, flowing a driving current to the thermoelectric module to control the object of temperature control to a target temperature, which is characterized by including detecting a temperature of the other surface of the thermoelectric module while obtaining a temperature difference from Seebeck voltage generated from a temperature difference between one surface and the other surface of the thermoelectric module brought into a state where the driving current is not flown; and controlling a temperature of the object of temperature control to a target temperature by controlling a direction and an amount of the driving current flown to the thermoelectric module according to the temperature difference between one surface and the other surface of the thermoelectric module and the temperature of the other surface.
A ninth aspect of the present invention resides in a temperature control method that is characterized in that, in the eighth aspect, the detection of the temperature difference of the thermoelectric module and the supply of the driving current to the thermoelectric module are alternately repeated.
A tenth aspect of the present invention resides in a temperature control method that is characterized in that, in the eighth or ninth aspect, the object of temperature control is an ink-jet head.
An eleventh aspect of the present invention resides in a temperature control method that is characterized in that, in any one of the eighth to tenth aspects, a radiator is air-tightly adhered to the other surface of the thermoelectric module.
A twelfth aspect of the present invention resides in a temperature control method that is characterized in that, in any one of the eighth to eleventh aspects, a P-type thermoelectric element and an N-type thermoelectric element are connected in series or in serial parallel in the thermoelectric module.
In such an invention, temperature control with high accuracy can be applied to an object of temperature control, and at the same time, removal of the object of temperature control is facilitated to thereby reduce costs at the time of replacement.